iwlwifi: pcie: NULLify pointers after free

Remember that those pointers have been freed by setting them
to NULL. Otherwise, we'd keep rxq pointing to random memory
which would prevent us from trying to re-allocate the Rx
resources if we call rx_alloc again.

Also, propagate the allocation failure to the caller of
iwl_pcie_nic_init so that we won't go further in the
start flow.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210210135352.996b400d2f1c.I630379c504644700322f57b259383ae0af8d1975@changeid


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>